International Patent Application No WO 96/31528 (Boden et al.) describes novel rationally designed peptides which self-assemble in one dimension to form beta sheet tape-like polymers. The tapes above a critical peptide concentration (typically above 0.3% v/v peptide) become physically entangled and gel their solutions in organic solvents or in water (FIG. 1). The peptide gels possess the specific property of being programmable to switch from the gel state to a fluid or stiffer gel state in response to external chemical or physical triggers.
It has recently been found that the tapes having chemically distinct opposing surfaces can give rise to an hierarchy of other self-assembled, supramolecular structures as a function of increasing peptide concentration: ribbons (two stacked tapes), fibrils (many ribbons stacked together) and fibres (entwined fibrils) [1-3] (FIG. 2). All these beta-sheet polymers appear twisted because of the peptide chirality. A theoretical model has been developed which rationalises this self-assembly process of beta-sheet forming peptides using a set of energetic parameters εj (FIG. 1). The magnitudes of εj define the peptide concentration ranges over which each type of polymer will be stable.